Protecting means for ionic valves



June 7, 1938. u. LAMM 2,119,865

PROTECTING MEANS FOR IONIC VALVES Filed Oct. 22, 1935' 3 Sheets-Sheet lf'r'g/ June 7, 1938. u. LAMM 2,119,865

PROTECTING MEANS on IONIC VALVES Filed Oct. 22, 1935 5 Sheets-Sheet 2 Jmen Zor U/za Lop/ram June 7, 1938. u. LAMM PROTECTING MEANS FOR IONICVALVES Filed Oct. 22, 1935 3 Sheets-Sheet 3 ]/1 yen for UHOLa/nm er wifi Patented June 7, 1938 UNITED STATES PATENT OFFICE PROTECTING MEANSFOR IONIC VALVES Application October 22, 1935, Serial No. v46,113

. In SwedenOctober 22, 1934 5 Claims. (Cl. 175-363) tacles of their own.Pure electronic relays, gen-.

erally called "hard relay tubes, are however 0 little suitable for suchpurposes for several reasons, and ion valve tubes, that is so-calledsoft hot cathode tubes with inert gas filling which during a long timemust be kept ready for operation, that, is, with the cathode heated, but15 not operate, show a marked tendency to harden, that is, to loosetheir filling of inert gas which may result in a failure when theirfunction is necessary.

On the other hand, a relay of the ionic valve type offers the advantagebefore a mechanical relay that its function will be much more rapid, andin order to utilize this advantage and at the same time toavoid theinconvenience adhering in separate valve tubes, there is accord- 25 ingto the present invention employed as a relay one or moreauxiliary valvepaths in the main valve vessel.

ing drawings in Figs. 1-4.'

the ionic valve, 2 its main anodes and 3 thegrids thereof. In Fig. 1,the latter ones are con-' nected not only to individual conductors 4, by

which for instance control voltages for diiierent purposes may beimpressed, but also over glow lamps 5 to a grid busbar 6 forlimpressinga blocking voltage common to all the grids. The

critical voltage of the glow lamps 5, below which they act as largeresistances, should lie so high .10 in relation to the individualcontrol voltages as to enable the latter to act independently of oneanother to a certain extent. The blocking voltage impressed on the gridbusbar must, on the contrary, be higher than the critical voltage of theglow lamps as only the difference between these voltages acts as anefiective blocking voltage on the grids.

The voltage impressed on the bar 6 is in this form obtained from a D. C.current source indicated as a battery I, the negative pole of which isconnected to the bar over a relay l3, which will be described in detailhereinafter, while its positive pole is connected to an auxiliary anode9 inthe main valve vessel, said anode being provided with a grid 8. Thegrid busbar is also negative voltage sufficient for the blocking.

Four forms of the invention are diagrammatically illustrated in theaccompany- In all the figures, l designates the cathode of connected tothe cathode over a large resistance It. Normally the anode 9 is blockedby means of the grid 8 whence the grid busbar 6 is kept at cathodepotential. When the anode 9 is released it will, on the contrary, obtainnearly the cathode potential (which in the following is counted as zeropotential in the usual manner), and the bar 6 will then (if the relay I3is closed) obtain a negative potential corresponding to that of thevoltage source I. The said negative potential is presumed to besufficient for preventing the ignition of the main anodes next time there spective anode voltages reach the values otherwise suflicienttherefor.

The release of the grid 8 is in this form effected by means ,of avoltage drop impulse from the D. C. side of the ionic valve, when thevoltage on this side breaks down as a consequenci of a short-circuit ora back-arcing. Between the D. C. terminals is connected a resistance IIfrom which the grid 8 normally obtains a certain In parallel to aportion of this resistance adjacent to the negative terminal isconnected a condenser l2 which, on the breakdown of voltage, maintainsthe voltage on this portion during a certain time whereby the lowerterminal of the condenser and thus also the connection point of the grid8 to the resistance will obtain a positive voltage. If the design of thegrid and the conditions of operation in the valve are such that theanode is released, at zero potential of the grid, the condenser I2'maybe omitted.

When the anode 9 is released it impresses, as already mentioned, anegative blocking potential on the main grids and thereby successivelyextinguishes the main anodes. As soon as this has occurred, the gridswill, however, cease to draw any current, but for maintaining theblocking potentialduring so long time that the conditions in the valvemay stabilize for continued normal operation (by deionization etc.), theanode 9 should still continue to carry current during a certain spaceof. time. This is possible thanks to the resistance III which then loadsthe auxiliary valve path sufllciently for maintaining the arc.

As soon as the conditions in the main valve paths have become normalagain, the auxiliary valve path shall be extinguished, and this iseffected by means of the aforesaid relay l3. This relay is energizedfrom a combination of current transformers ll, connected withprimarywind-.

ings in the A. C. conductors of the rectifier or secondary circuits ofthe current transformers,

then cuts off the current so that also the anode 9 will be extinguished.This should, however, take place with a certain retardation which may beobtained by the aid of a condenser 18 connected in parallel to the relaycoil, said condenser being loaded to the voltage between the coilterminals and being unloaded through the coil when the current from thecurrent transformer ceases. In order that the said condenser shall notretard the energizing of the relay if the load for instance risesrapidly from below load to a value causing risk of back-arcing, asmall'rectifler I ll with incomplete valve action is connected in serieswith the condenser IS in such a manner as to enable the condenser to berapidly discharged but only slowly charged.

A particular advantage of the said arrangement of a current responsiverelay in the auxiliary valve path is that the blocking device isprevented from functioning inthe case that an ionic valve operating assingle rectifier should be extinguished at low load. Such an extinctioncauses, as well as a short-circuit or a backarcing, a disappearing ofthe voltage on the D. C. side, but since the relay I3 then keeps thecircult through the anode 9 interrupted, no grid blocking will resultfrom this.

In Fig. 2, no individual control of the main grids 3 is provided for,whence it is not necessary to introduce special voltage blocking betweenthese grids and the grid busbar 6. As a voltage source of the auxiliaryvalve path through the anode 9 serves a condenser 20 which is keptloaded by means of a transformer 2| in series with a; rectifier 22.Between the terminals of the transformer may also be connected a. largeloading resistance 23 for smoothing the voltage. The releasing impulsefor the grid 8 of the anode 9 is here obtained from the A. C. side as a'consequence of the rapid change of voltage in positive direction whicha. back-arcing anode is subjected to, being transferred from a negativepotential, generally near the maximum value, to nearly cathodepotential. For accomplishing this, the grid is connected to a busbar 24which over condensers 25 is connected to the conductors of all the mainanodes. Normally the potential of the grid is determined by the factthat it is con-- nected to the negative pole of a D. C. voltage in thepositive'direction to a value near the cath-v ode potential, thecorresponding.' condenser discharges through the grid 8 andthereby.impresses a positive potential on the latter. v V s In this figure, nodevice is shown for maintaining the current through'the auxiliary anode9, after the main anodes have been extinguished and their grids havetherefore ceased-to, draw an It will.

appreciable current. There is instead a special arrangement formaintaining, during a certain period thereafter, the positive voltage onthe grid- 8. The result will be the same because such a voltage onthegrid implies that the anode is kept in leading connection with theionized vapor and is thus prevented from assuming an appreciablepositive potenial, and on account of the interconnected voltage source(the condenser 20) it then keeps the main grids negative. Thearrangement for maintaining the positive voltage cn the grid 8 mainlyconsists of a transformer 21, the primary winding of which is connectedin the conductor leading to the anode 8 preferably as a shunt to aresistance 28, while its secondary winding is connected between thecathode and the grid 8 in parallel to a condenser 29. When the anode 9draws a current from the condenser 20, the condenser 29 issimultaneously charged over the transformer 21, and then it is preventedby a rectifier 29a from discharging the same way. Therefore, it insteaddischarges over the grid 8 and is assumed to be so dimensioned as tokeep the grid positive during so long time as is necessary for removingthe consequences of the disturbance. The rectifier 29a. should admit somuch back current as not to prevent the negative charging of the grid 8from the voltage source-26 in normal operation. The transformer 27 mayinstead be so connected as to charge the condenser 28, when the currentin the anode 9 decreases, in which case the resistance 28 should bereplaced by an inductance which may form part of the transformer.

In Fig. 3, the auxiliary anodes 9 are three in number and connectedtothe grid busbar 6 over a three-phase transformer 30 which serves as avoltage source for the blocking voltage on the main grids 3. The grids 8of the auxiliary anodes are normally blocked by being connected to apotentiometer resistance 3| on the D. C. side and obtain their releasingvoltage impulse from the A. C. side when an overcurrent occurs on thelatter. The alternating current, by a combination of currenttransformers I4 and rectiflers I of the same kind as that shown in Fig.1, acts on a load resistance 32, which is connected between the cathodeand the grids 8 in series with av glow lamp 33. The difference betweenthe voltage on the resistance 32 and the voltage absorbed by the glowlamp 22 is thus impressed on the grids, and the arrangement is sodimensioned that this diflerence of voltage will be suflicient forreleasing the anodes 9 only when the alternating current exceeds thepermissible value. A condenser 34 may be connected in parallel to theresistance and the glow lamp for maintaining the voltage on the gridsalso after the alternating current has been reduced by the blockingaction of the main grids.

- obvious means of separating the auxiliary anode 9 from the maincurrent paths.

The different methods illustrated for obtaining the primary gridblocking impulse, and the voltage cn the main grids, for maintaining andfinal- 1y extinguishing the current in the auxiliary valve path may ofcourse be combined with one another in other ways than those described.Also the arrangement for individually controlling the main grids may ofcourse be employed in combination with any of the devices otherwisedescribed.

A particular advantage of arranging the auxiliary valve path or paths inthe main valve vessel besidesthose already mentioned, is that theconditions for ignition of the auxiliary anode will depend to a certainextent on the current of the main anodes. Thus it is for instancepossible, by suitably adapting the screening of the auxiliary anode, tocause the latter not to be ignited even at a certain positive gridvoltage if the main anodes operate at low load. Hereby a greater freedomin the choice in voltage source for the grid of the auxiliary anode isObtained. as an unintentional release at low load, which otherwise mayhappen on account of an instability in the arc, can at any rate besafely precluded. It may even under certain conditions be possible toomit entirely the control voltage for the grid or screening device ofthe auxiliary anode, which may be ignited exclusively as a consequenceof the increased degree of ionization in the rest of the vessel causedby a disturbance, as a back-arcing or an overload. It is known, that theignition voltage of an anode provided with a screening device is afunction not only of the potential of the screening device, but also ofthe temperature and degree of ionization of the conducting gaseousmedium, said latter factors depending in their turn partly on thecurrent strength of the .adjacent anodes, partly on the degree ofscreening against these. By adapting this screening in an appropriatemanner, it is possible to keep the auxiliary anode blocked at constantgrid voltage or even without a particularly impressed grid voltage aslong as the total current in the vessel is kept below a certainpermissible value, but automatically to release itas soon as this valueis exceeded. The auxiliary anode or anodes should in such a case, invessels containing several anodes, preferably be symmetrically arrangedwith respect to the anodes, for instance centrally in the vessel asshown at Fig. 4.

Independently of the place of the auxiliary anode, it may be desirableto keep it at a higher it should, however, be screened by a separatesleeve.

I claim as my invention '1. In ionic discharge valves, a valve vessel, acathode and working anodes therein, grids for blocking said anodes, atleast one auxiliary anode in said vessel, grid control for saidauxiliary anode, means for impressing a blocking voltage on the grids ofsaid working anodes over said auxiliary anode, and means for releasingthe grid control of said auxiliary anode on the occasion of adisturbance.

2. In ionic discharge valves, a valve vessel, a cathode and workinganodes therein, grids for blocking said anodes, atleast one auxiliaryanode in said vessel, grid control for said auxiliary anode, means forreleasing said grid control, a current path leading from a source ofblocking voltage over said auxiliary anode to the grids of said workinganodes and a current pathnleadingin parallel to said path from saidauxiliary anode to the catlrode over said source of blocking voltage anda re sistance.

3. In ionic discharge valves, a valve vessel, a cathode and workinganodes therein, grids for blocking said anodes, at least one auxiliaryanode in said vessel, grid control for said auxiliary anode, means forreleasing said grid control, a current path leading from a source ofblocking voltage over said auxiliary anode to the grids of saidworkinganodes, a current path leading in parallel to said path from saidauxiliary anode to the cathode over said source of blocking voltage anda resistance, and. means for automatically interrupting the currentthrough said auxiliary anode at the cessation of the disturbance.

4. In ionic discharge valves, a valve vessel, a cathode and workinganodes therein, grids for blocking said anodes, at least one auxiliaryanode in said vessel, a control gride for said auxiliary anode, meansfor impressing a blocking voltage on the grids of said working anodesover said auxiliary anode, means for impressing a positive voltage onthe control grid of said auxiliary anode on the occasion of adisturbance, and means for maintaining said positive voltage after saidworking anodes have been extinguished as a consequence of the saidblocking.

5. In ionic discharge valves, a valve vessel, a

cathode and working anodes therein, grids for blocking said anodes, atleast one auxiliary anode in said vessel, a screen separating said anodefrom the main current paths, means for impressing such a potential onsaid screen as to block the auxiliary anode as long as the total currentin said vessel is kept below a certain value but to release said anodeas soon as this value is exceeded, and a currentv path leading over saidauxiliary anode to the grids for the working anodes for impress-- ing ablocking voltage on said grids.

UNO mm

